In general, a wireless sensor network (WSN) consists of a set of sensor nodes S1, S2, . . . SK which are centrally controlled by means of a central controller C, which in the following is also referred to as WSN controller. The sensor nodes S1, S2, . . . SK are deployed over a geographical area. Each sensor or sensor node S1, S2, . . . SK by measurement collects information about a physical phenomenon and forwards its measurement result via a wireless link to the WSN controller C for further processing. Since the costs of the sensor nodes S1, S2, . . . SK should be reduced and the sensor nodes are usually powered by batteries, the sensor design should aim to reduce the implementation complexity and the power consumption. The central controller C, however, does not have the same limitations on cost and power. Therefore, in order to enhance the performance of a WSN, methods and functions should be identified that can mainly be implemented at the central controller C and avoid increasing the complexity of sensor nodes S1, S2, . . . SK.
R. Laroia, P. Visawanath, and D. Tse have described in “Opportunistic beamforming using dumb antennas”, IEEE Trans. Inform. Theory, vol. 48, pp. 1277-1294, 2002, the concept of opportunistic beamforming with dumb antennas for the downlink in a cellular mobile communication system for exploiting multi-user diversity and suppressing adjacent cell interference. The scheme uses multiple antennas at the basestation to transmit the same signal from each antenna modulated by a complex gain whose value is changing in a controlled, but random fashion. Each mobile user measures the signal-to-interference-plus-noise ratio (SINR) by tracking a pilot signal that is repeatedly radiated at the transmit antennas of the basestation. All mobile users feed back their measurements to the basestation which analyzes the fed-back SINRs values in order to form a rule for efficiently scheduling a downlink message transfer to the mobile users.